Conventional bicycles comprise pedals that are mounted on an axle of a bottom bracket and consequently are guided by way of the bottom bracket. The drive of the conventional bicycle is provided by virtue of the fact that the pedals are rotated about the bottom bracket axle and this rotational movement is transferred directly to a drive wheel, by way of example by way of pinion and chain. The power that a rider applies by means of muscle power onto the pedals is consequently passed directly on to the drive wheel so that the drive of the bicycle that the rider can perceive corresponds to the effort that is expended by said rider, namely the muscle power that said rider provides. In accordance with hybrid bicycles of the generic type that are driven by means of muscle power and electrical energy, in contrast the drive wheel is not driven directly by means of the pedals but rather at least in part by means of an electric drive motor. In the case of series hybrid bicycles, the drive of the drive wheel is provided solely by means of an electric drive motor that is supplied with electrical energy. The pedals in contrast solely operate a generator so that electrical energy is generated by means of muscle power, said electrical energy being supplied selectively to the battery and/or the drive motor.
In the case of hybrid bicycles in accordance with the generic type, it is necessary to always intelligently control the drive motor so that the drive power that the drive motor supplies to the drive wheel corresponds to the drive power that the rider desires and that the rider typically—as said rider is used to in conventional bicycles—would like to simulate by way of consciously using his muscle power on the pedals.
The exact correlation between the torque of the drive wheel and the pedal torque that is applied by the rider while maintaining a constant translational ratio is however only inadequately achieved in the case of series hybrid bicycles of the generic type. By way of example, hybrid bicycles are thus known in which the drive motor is always connected to a drive power that is constantly predetermined by the rider if the control device of the hybrid bicycle detects an actuation of the pedals. As a consequence, however, it is not possible to predetermine the drive power at the drive wheel by means of the drive motor in dependence upon the situational desire of the rider, said drive power being predetermined by way of the muscle power of said rider on the pedals. Moreover, hybrid bicycles are known in which the pedal torque that a rider applies to the pedals and that correlates directly with the muscle power that is applied over the length of the crank arm of the bottom bracket is determined with the aid of a generator that is driven by means of the pedals. The drive torque of the drive motor is then set directly proportional to the pedal torque that is determined by way of the generator while maintaining a constant rotational speed translation. Although such hybrid bicycles of the generic type can render possible in certain operating situations a sufficient correlation between drive power that prevails at the drive wheel and the rider power that is applied by way of muscle power by means of the rider, this correlation is in fact broken at least in extreme situations by way of example in the case of the pedals being influenced with a torque that exceeds the maximum torque of the generator such as by way of example when setting off or sprinting. Since in the case of the described hybrid bicycles of the generic type the drive power can only be proportional to the rider power that is applied for as long as the generator is influenced with a pedal torque that is lower than its maximum generator torque, in such extreme situations the rider finds that when applying a particularly intense muscle power, it is not possible to generate an accordingly particularly intense propulsion of the hybrid bicycle.